The present invention relates to an ink-jet recording head, its manufacturing method and an ink-jet recording device wherein a piezoelectric element is formed in a part of a pressure generating chamber communicating with a nozzle aperture for jetting an ink droplet via a diaphragm so that an ink droplet is jetted by the displacement of the piezoelectric element.
For an ink-jet recording head wherein a part of a pressure generating chamber communicating with a nozzle aperture for jetting an ink droplet is constituted by a diaphragm and an ink droplet is jetted from the nozzle aperture by deforming the diaphragm by a piezoelectric element and pressurizing ink in the pressure generating chamber, two types of a type that a piezoelectric actuator in a longitudinal vibration mode for extending or contracting a piezoelectric element axially is used and a type that a piezoelectric actuator in a flexural vibration mode for bending a piezoelectric element is used are realized.
For the former, the volume of a pressure generating chamber can be varied by touching the end face of a piezoelectric element to a diaphragm and a head suitable for high density printing can be manufactured, however, on the other hand, there is a problem that a difficult process for cutting a piezoelectric element in the form of the tooth of a comb in accordance with the arrangement pitch of nozzle apertures and work for positioning and fixing the cut piezoelectric element over a pressure generating chamber are required and its manufacturing process is complicated.
In the meantime, for the latter, a piezoelectric element can be fixed on a diaphragm in a relatively simple process for sticking a green sheet which is piezoelectric material in accordance with the shape of a pressure generating chamber and burning it, however, on the other hand, there is a problem that area to some extent is required because flexural vibration is utilized and high density arrangement is difficult.
In the meantime, to solve the problem of the recording head equivalent to the latter, as disclosed in Japanese published unexamined patent application No. Hei5-286131, a recording head wherein a piezoelectric element is independently formed every pressure generating chamber by forming a uniform piezoelectric material layer on the whole surface of a diaphragm by thin film technique and cutting the piezoelectric material layer in a shape corresponding to each pressure generating chamber by lithography is proposed.
Hereby, there is an advantage that work for sticking a piezoelectric element on a diaphragm is not required, not only a piezoelectric element can be fixed by a precise and convenient method such as lithography but the piezoelectric element can be thinned and high speed driving is enabled. In this case, a piezoelectric element corresponding to each pressure generating chamber can be driven by providing at least only an upper electrode every pressure generating chamber with a piezoelectric material layer provided on the whole surface of a diaphragm.
In the recording head using such a piezoelectric actuator in a flexural mode, a lead electrode for supplying voltage for driving a piezoelectric element corresponding to each pressure generating chamber is provided corresponding to each pressure generating chamber.
However, as described above, there is a problem that large stress is readily caused by the driving of a piezoelectric element in a connection (hereinafter called a contact) between a piezoelectric element corresponding to each pressure generating chamber and a lead electrode, and a crack and breaking may be caused.
There is also a problem that as a lead electrode is connected to a contact, displacement by applying voltage is small, compared with that in another part, however, nevertheless, as compliance is not small, compared with that in another part, jetting speed is deteriorated and driving voltage is increased.
Further, there is a problem that a crack is readily made in a piezoelectric layer in the vicinity of such a contact hole.
There is also a case that a piezoelectric element is sequentially pulled out over the peripheral wall of a pressure generating chamber to supply voltage for driving each piezoelectric actuator, however, in this case, there is a problem that a crack is readily made in a part in which a piezoelectric element crosses a boundary between a pressure generating chamber and the peripheral wall of a piezoelectric layer.
In the meantime, in the above ink-jet recording head, structure in which a diaphragm in a part corresponding to both sides in the direction of the width of a piezoelectric element is thinned is proposed to enhance the efficiency of the displacement of a diaphragm by the driving of the piezoelectric element. However, if displacement is increased as described above, a tendency that breaking such as a crack is readily caused particularly in the vicinity of the above peripheral wall of a pressure generating chamber or in the vicinity of a contact hole is promoted.
The problem that jetting speed is deteriorated and driving voltage is increased and the problem that breaking such as a crack is readily caused in the vicinity of the peripheral wall of a pressure generating chamber or in the vicinity of a contact hole come into question particularly in case a piezoelectric material layer is formed by film forming technique. That is, it is because a piezoelectric material layer formed by film forming technique is very thin and the rigidity is low, compared with that of a piezoelectric material layer in which a piezoelectric element is stuck.
The present invention is made in view of such a situation and the object is to provide an ink-jet recording head, its manufacturing method and an ink-jet recording device wherein a crack, breaking and others due to stress concentration in a contact are prevented and the efficiency of displacement in the contact can be prevented from being deteriorated.
The present invention is made in view of such a situation and the object is to provide an ink-jet recording head, its manufacturing method and an ink-jet recording device wherein a crack and others in a piezoelectric element, in the vicinity of the peripheral wall of a pressure generating chamber of a piezoelectric layer and in the vicinity a contact hole are prevented and durability can be secured.
A first embodiment of the present invention to solve the above problems relates to an ink-jet recording head based upon an ink-jet recording head wherein plural pressure generating chambers each of which communicates with a nozzle aperture are formed and a piezoelectric element at least including a lower electrode, a piezoelectric layer and an upper electrode is formed in an area corresponding to one of the plural pressure generating chambers and characterized in that a connection between a lead electrode for applying voltage to the piezoelectric element and the piezoelectric element is provided in an area opposite to a passage communicating with the pressure generating chamber other than the area opposite to the above pressure generating chamber.
According to such a first embodiment, as the connection between the lead electrode and the piezoelectric element is formed in an area other than the area opposite to the pressure generating chamber, the quantity of displacement of the pressure generating chamber by the piezoelectric element can be increased.
A second embodiment of the present invention relates to an ink-jet recording head based upon the first embodiment and characterized in that a narrow part which communicates with the end far from the above nozzle aperture of the above pressure generating chamber and at least one of the width and the depth of which is smaller than that of the pressure generating chamber and a communicating part which communicates with the pressure generating chamber via the narrow part are provided and a connection between the above piezoelectric element and the above lead electrode is provided in an area opposite to the above communicating part.
According to such a second embodiment, as the connection to the lead electrode is formed in a position opposite to the communicating part which communicates with the pressure generating chamber via the narrow part, deformation is hardly made in the connection, the breaking of the piezoelectric layer and others in the vicinity of the connection is avoided and displacement is not deteriorated by the connection.
A third embodiment of the present invention relates to an ink-jet recording head based upon the second embodiment and characterized in that the width of the above narrow part is formed so that it is narrower than the width of the above pressure generating chamber, the above upper electrode is independently formed every area opposite to the pressure generating chamber so that it is narrower than the width of the pressure generating chamber and formed so that the upper electrode continues to a part provided in an area opposite to the above communicating part via a narrow lead provided in a part opposite to the narrow part.
According to such a third embodiment, even if voltage is applied via the lead electrode, the breaking of the piezoelectric layer and others is avoided without concentrating stress on the piezoelectric layer in the narrow part and the communicating part and the pressure generating chamber can be effectively displaced.
A fourth embodiment of the present invention relates to an ink-jet recording head based upon the second embodiment and characterized in that the width of the above narrow part is formed so that it is narrower than the width of the above pressure generating chamber, the above upper electrode is independently formed every an area opposite to the pressure generating chamber so that it is narrower than the width of the pressure generating chamber and formed so that the upper electrode continues to a part provided in an area opposite to the above communicating part via the narrow lead provided in a part opposite to the narrow part, the above piezoelectric layer is formed corresponding to the upper electrode over the pressure generating chamber and extended to an area corresponding to the narrow part and the communicating part in approximately the same width.
According to such a fourth embodiment, as the piezoelectric layer is provided up to a position opposite to the outside of a passage in an area opposite to the narrow part, the displacement of the piezoelectric layer particularly in the narrow part and a boundary between the pressure generating chamber and the communicating part can be further reduced and the breaking of the piezoelectric layer is further prevented.
A fifth embodiment of the present invention relates to an ink-jet recording head based upon the second embodiment and characterized in that the width of the above narrow part is formed so that it is narrower than that of the above pressure generating chamber, the above piezoelectric layer and the above upper electrode are independently formed every area opposite to the pressure generating chamber so that the width of them is narrower than that of the pressure generating chamber and formed so that the piezoelectric layer and the upper electrode continue to a part provided in the opposite area of the communicating part via a narrow lead provided in a part opposite to the narrow part.
According to such a fifth embodiment, the piezoelectric layer is provided opposite to the pressure generating chamber, the narrow part and the communicating part, however, even if voltage is applied via the lead electrode, displacement is hardly caused in the narrow part and the communicating part and the pressure generating chamber can be effectively displaced.
A sixth embodiment of the present invention relates to an ink-jet recording head based upon any of the third to fifth embodiments and characterized in that each boundary between the above lead formed narrowly and a part in an area opposite to the above pressure generating chamber and between the lead and a part in an area opposite to the above communicating part is formed in a radial form.
According to such a sixth embodiment, as the boundaries at both ends of the lead are respectively formed in a radial form, a crack and others are further difficult to cause.
A seventh embodiment of the present invention relates to an ink-jet recording head based upon any of the second to sixth embodiments and characterized in that said communicating part is composed of a common passage communicating with each pressure generating chamber via each narrow part.
According to such a seventh embodiment, vibration in the vicinity of the connection due to voltage applied from the lead electrode can be prevented and the generation of a crack and others of the piezoelectric element is further inhibited.
An eight embodiment of the present invention relates to an ink-jet recording head based upon any of the first to seventh embodiments and characterized in that an insulating layer provided with a window in a part corresponding to said connection to at least said lead electrode is formed on the upper surface of said upper electrode.
According to such an eighth embodiment, insulation between the upper electrode and the lower electrode and cutoff from the air can be secured by providing the insulating layer.
A ninth embodiment of the present invention relates to an ink-jet recording head based upon the eighth embodiment and characterized in that the above insulating layer is formed by silicon oxide, silicon nitride and organic material such as polyimide.
According to such a ninth embodiment, an insulating layer can be readily formed by a film forming process and a lithographic process for example.
A tenth embodiment of the present invention relates to an ink-jet recording head based upon an ink-jet recording head wherein plural pressure generating chambers respectively communicating with a nozzle aperture and a piezoelectric element including at least a lower electrode, a piezoelectric lay and an upper electrode in an area corresponding to the pressure generating chamber are formed and characterized in that a communicating part communicating with an ink supply port to which ink is supplied from the outside and the above pressure generating chamber communicate via a narrow part narrower than the width of the corresponding pressure generating chamber and the vicinity of the end on the side of the narrow part of the pressure generating chamber is provided with a narrow part the width of which is gradually narrowed.
According to such a tenth embodiment, the quantity of displacement of the piezoelectric element in a part corresponding to the narrow part is inhibited and the breaking and others of the piezoelectric layer are prevented. An eleventh embodiment of the present invention relates to an ink-jet recording head based upon the tenth embodiment and characterized in that the width of the above narrow part is in the range of 1 to 99% of the width of the above pressure generating chamber.
According to such an eleventh embodiment, the inflow of ink into the pressure generating chamber can be adjusted depending upon the width of the narrow part.
A twelfth embodiment of the present invention relates to an ink-jet recording head based upon the tenth or eleventh embodiment and characterized in that at least the above piezoelectric layer of the above piezoelectric element formed in an area opposite to the above pressure generating chamber is continuously extended from the area opposite to the pressure generating chamber to an area opposite to the above narrow part and the above communicating part.
According to such a twelfth embodiment, as the piezoelectric layer is extended to the area opposite to the narrow part and the communicating part, the breaking and others of the piezoelectric layer are prevented.
A thirteenth embodiment of the present invention relates to an ink-jet recording head based upon any of the tenth to twelfth embodiments and characterized in that a connection between a lead electrode for applying voltage to the above piezoelectric element and the corresponding piezoelectric element is provided in an area opposite to the above communicating part.
According to such a thirteenth embodiment, as the connection between the lead electrode and the piezoelectric element is formed in a position opposite to the communicating part, deformation is hardly caused in the connection and the breaking of the piezoelectric layer and others in the vicinity of the connection is avoided.
A fourteenth embodiment of the present invention relates to an ink-jet recording head based upon the twelfth or thirteenth embodiment and characterized in that the width of the above piezoelectric layer is narrower than that of the above narrow parts.
According to such a fourteenth embodiment, the displacement of the piezoelectric layer is not regulated in the direction of the width and no strong stress acts upon the piezoelectric layer.
A fifteenth embodiment of the present invention relates to an ink-jet recording head based upon any of the tenth to fourteenth embodiments and characterized in that a common ink chamber to which ink is supplied from the above ink supply port communicates with each communicating part.
According to such a fifteenth embodiment, ink supplied from the ink supply port is supplied to the pressure generating chamber via the common ink chamber and each communicating part.
A sixteenth embodiment of the present invention relates to an ink-jet recording head based upon any of the tenth to fourteenth embodiments and characterized in that the communicating part communicating with each pressure generating chamber is mutually connected to form a reservoir.
According to such a sixteenth embodiment, ink supplied from the ink supply port is supplied to the pressure generating chamber via the reservoir.
A seventeenth embodiment of the present invention relates to an ink-jet recording head based upon any of the first to sixteenth embodiments and characterized in that the above narrow part is formed through the passage forming substrate in which the above pressure generating chamber is formed.
According to such a seventeenth embodiment, as adjustment in the direction of the thickness is not required, the narrow part can be readily formed.
An eighteenth embodiment of the present invention relates to an ink-jet recording head based upon any of the first to seventeenth embodiments and characterized in that the above piezoelectric element is formed on an elastic film formed on the passage forming substrate in which the above pressure generating chamber is formed.
According to such an eighteenth embodiment, the elastic film is deformed by the piezoelectric element and pressure in the pressure generating chamber changes.
A nineteenth embodiment of the present invention relates to an ink-jet recording head based upon any of the first to eighteenth embodiments and characterized in that the above pressure generating chamber is formed by a silicon monocrystalline substrate by anisotropic etching and each layer of the above piezoelectric element is formed by a film forming method and a lithographic method.
According to such a nineteenth embodiment, an ink-jet recording head provided with high density nozzle apertures can be relatively readily manufactured in a large quantity.
A twentieth embodiment of the present invention relates to an ink-jet recording device characterized in that an ink-jet recording head according to any of the first to nineteenth embodiments is provided.
According to such a twentieth embodiment, an ink-jet recording device wherein the efficiency of the driving of the head is enhanced and ink can be satisfactorily jetted can be realized.
A twenty-first embodiment of the present invention relates to a method of manufacturing an ink-jet recording head based upon a method of manufacturing an ink-jet recording head wherein a piezoelectric element is formed in an area corresponding to the above pressure generating chamber by sequentially laminating a lower electrode layer, a piezoelectric layer and an upper electrode layer on an elastic film provided on one side of a passage forming substrate and patterning each layer and the above passage forming substrate is etched from the other side so as to form a pressure generating chamber communicating with a nozzle aperture and characterized in that a step for forming a narrow part which communicates with one end of the above pressure generating chamber and which is narrower than the width of the corresponding pressure generating chamber by piercing the above narrow part by etching the above passage forming substrate is provided.
According to such a twenty-first embodiment, as adjustment in the direction of the thickness of the narrow part is not required, the narrow part is readily formed.
A twenty-second embodiment of the present invention relates to a method of manufacturing an ink-jet recording head based upon the twenty-first embodiment and characterized in that a step for forming the above narrow part is simultaneously executed with a step for forming the above pressure generating chamber by etching.
According to such a twenty-second embodiment, the narrow part can be readily formed without increasing the number of manufacturing processes.
A twenty-third embodiment of the present invention relates to a method of manufacturing an ink-jet recording head based upon the twenty-first or twenty-second embodiment and characterized in that the above pressure generating chamber is formed by a silicon monocrystalline substrate by anisotropic etching and each layer of the above piezoelectric element is formed by a film forming method and a lithographic method.
According to such a twenty-third embodiment, an ink-jet recording head provided with high density nozzle apertures can be relatively readily manufactured in a large quantity.